Crematogaster mimosae

Crematogaster mimosae
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Crematogastrini
Genus:	Crematogaster
Species:	C. mimosae
Binomial name
Crematogaster mimosae Santschi, 1914 Specimen Labels

One of four ant species (also Crematogaster nigriceps, Crematogaster sjostedti, Tetraponera penzigi) that live on Vachellia drepanolobium. This small arboreal ant assemblage, nesting in this dominant Africa savanna tree, have been the subject of intensive research by a large group of ecologists studying species interactions and species co-existence (e.g., Young et al. 1997; Martins 2010).

At a Glance

• Ant-plant specialist

Identification

Keys including this Species

• Key to Arabian Crematogaster

Distribution

Sharaf et al. (2019): Initially described from Kenya, in the Afrotropics this species is East African in its distribution found in Kenya, Uganda, Somalia, Sudan, and Tanzania (Guénard et al. 2017; Janicki et al. 2017). In the Arabian Peninsula, it was recorded from the KSA, Oman, the UAE and Yemen (Collingwood 1985, Collingwood and Agosti 1996; Borowiec 2014; Sharaf et al. 2018).

Latitudinal Distribution Pattern

Latitudinal Range: 22.816667° to 15.469444°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: AntMaps

Distribution based on Regional Taxon Lists

Afrotropical Region: Kenya (type locality), Saudi Arabia, United Arab Emirates, Yemen.
Palaearctic Region: Oman.

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

C. mimosae depends on the domatia provided by the plant for brood rearing and are never found free living separately from the acacias. Ants patrol all parts of the tree above the ground and directly prey on invertebrates and repel browsing herbivores.

Workers tend phloem-feeding scale insects, presumably imposing a cost on host plants that partly offsets the protection given against mammalian herbivores. Trees occupied by C. mimosae had significantly less browsing by giraffes and black rhino than trees occupied by other ant species (Martins 2010).

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  Swollen thorns of Vachellia drepanolobium inhabited by Crematogaster. From Kitengela, Kenya. Photo by Christian Peeters.
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  Swollen thorns of Vachellia (Acacia) drepanolobium.
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  C. mimosae workers and brood inside a domatia (swollen thorn), showing also carton partitions. Photo by Christian Peeters.

Explore Vachellia drepanolobium  Vachellia drepanolobium, more commonly known as Acacia drepanolobium or whistling thorn, is a swollen-thorn acacia native to East Africa. The whistling thorn grows up to 6 meters tall. It produces a pair of straight spines at each node, some of which have large bulbous bases. These swollen spines are naturally hollow and occupied by any one of several symbiotic ant species. The common name of the plant is derived from the observation that when wind blows over bulbous spines in which ants have made entry and exit holes, they produce a whistling noise. Symbiosis with ants Like other acacias, whistling thorns have leaves that contain tannins, which are thought to serve as deterrents to herbivory. Like all African acacias, they are defended by spines. In addition, whistling thorn acacias are myrmecophytes that have formed a mutualistic relationship with some species of ants. In exchange for shelter in the bulbous spines (domatia) and nectar secretions, these ants appear to defend the tree against herbivores, such as elephants and giraffes, as well as herbivorous insects. At a site in Kenya, three Crematogaster and one Tetraponera ant species compete for exclusive possession of individual whistling thorn trees: Crematogaster mimosae, Crematogaster sjostedti, Crematogaster nigriceps and Tetraponera penzigi (Young et al., 1996; Palmer et al., 2008). Ant species vary in their level of mutualism with whistling thorn trees. The most common ant symbiote (~ 50% of trees), C. mimosae, has the strongest mutualistic relationship, aggressively defending trees from herbivores while relying on swollen-spines for shelter and feeding from nectar produced by glands near the base of leaves. Because the ants compete for exclusive usage of a given tree, some species employ tactics to reduce the chance of a hostile ant invasion. Crematogaster nigriceps trim the buds of trees to reduce their lateral growth, thereby reducing chances of contact with a neighbouring tree occupied by a rival colony. Tetraponera penzigi, the only species which does not utilise the nectar produced by the trees, instead destroys the nectar glands to make a tree less appealing to other species. The symbiotic relationship between the trees and the ants appears to be maintained by the effects of browsing by large herbivores. At the site in Kenya, when large herbivores were experimentally excluded, trees reduced the number of nectar glands and swollen spines they provided to ants. In response, the usually dominant C. mimosae increased their tending of parasitic sap-sucking insects as a replacement food source. In addition, the number of C. mimosae-occupied trees declined while twice as many become occupied by C. sjostedti, a much less aggressive defender of trees. Because C. sjostedti benefits from the holes made by boring beetle larvae, this species facilitates parasitism of trees by the beetles. As a result, the mutualistic relationship between whistling thorn trees and resident ants breaks down in the absence of large herbivores, and trees become paradoxically less healthy as a result (Palmer et al., 2008) and become much more vulnerable should herbivores be reintroduced. References Palmer, T.M., Stanton, M.L., Young, T.P., Goheen, J.R., Pringle, R.M., Karban, R. 2008. Breakdown of an Ant–Plant Mutualism Follows the Loss of Large Herbivores from an African Savanna. Science 319(5860): 192–195 (doi:10.1126/science.1151579). Young, T.P., Stubblefield, C.H., Isbell, L.A. 1996. Ants on swollen-thorn acacias: Species coexistence in a simple system. Oecologia 109(1): 98–107 (doi:10.1007/s004420050063).

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• mimosae. Crematogaster mimosae Santschi, 1914b: 87, fig. 11 (w.) KENYA.
  • Type-material: syntype workers (number not stated).
  • Type-locality: Kenya (“Afrique orientale anglaise”): Mt Kenya, 2000 m., xi.1908 (Ch. Alluaud).
  • Type-depository: NHMB.
  • [Misspelled as mimosea by Santschi, 1937a: 55.]
  • Menozzi, 1939c: 105 (q.).
  • Combination in C. (Crematogaster): Wheeler, W.M. 1922a: 841;
  • combination in C. (Acrocoelia): Emery, 1922e: 148;
  • combination in C. (Crematogaster): Bolton, 1995b: 166.
  • Status as species: Emery, 1922e: 148; Wheeler, W.M. 1922a: 841; Menozzi, 1930b: 95; Menozzi, 1939c: 104; Collingwood, 1985: 261; Bolton, 1995b: 157; Collingwood & Agosti, 1996: 331; Hita Garcia, et al. 2013: 211; Borowiec, L. 2014: 67 (see note in bibliography); Sharaf, Aldawood & Hita Garcia, 2019: 68.
  • Distribution: Kenya, Oman, Saudi Arabia, Somalia, Sudan, Tanzania, Uganda, United Arab Emirates, Yemen.
  • Current subspecies: nominal plus tenuipilis.
  • minchini. Crematogaster minchini Rothney, 1903: 98. Nomen nudum.

Taxonomic Notes

Sharaf et al. (2019): From a taxonomic perspective, this is one of the “easy” cases within the genus in Arabia, thus very straightforwardly identifiable.

References

• Borowiec, L. 2014. Catalogue of ants of Europe, the Mediterranean Basin and adjacent regions (Hymenoptera: Formicidae). Genus (Wroclaw) 25(1-2): 1-340.
• Emery, C. 1922c. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [part]. Genera Insectorum 174B: 95-206 (page 148, Combination in C. (Acrocoelia))
• Martins, D.J. 2010. Not all ants are equal: obligate acacia ants provide different levels of protection against mega-herbivores. African Journal of Ecology 48, 1115–1122 (doi:10.1111/j.1365-2028.2010.01226.x).
• Menozzi, C. 1939c. Hymenoptera Formicidae. Missione Biol. Paese Borana 3: 97-110 (page 105, queen described)
• Santschi, F. 1914b. Voyage de Ch. Alluaud et R. Jeannel en Afrique Orientale, 1911-1912. Résultats scientifiques. Insectes Hyménoptères. II. Formicidae. Paris: Libr. A. Schulz, pp. 41-148. (page 87, fig. 11 worker described)
• Sensenig, R. L., D. K. Kimuyu, J. C. Ruiz Guajardo, K. E. Veblen, C. Riginos, and T. P. Young. 2017. Fire disturbance disrupts an acacia ant–plant mutualism in favor of a subordinate ant species. Ecology. 98:1455-1464. doi:10.1002/ecy.1797
• Sharaf, M.R., Aldawood, A.S., Hita Garcia, F. 2019. Review of the Arabian Crematogaster Lund (Hymenoptera, Formicidae), synoptic list, distribution, and description of two new species from Oman and Saudi Arabia. ZooKeys 898: 27–81 (doi:10.3897/zookeys.898.37531).
• Ward, P.S., Downie, D.A. 2005. The ant subfamily Pseudomyrmecinae (Hymenoptera: Formicidae): phylogeny and evolution of big-eyed arboreal ants. Systematic Entomology 30:310-335 (doi:10.1111/j.1365-3113.2004.00281.x).
• Wheeler, W. M. 1922j. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bull. Am. Mus. Nat. Hist. 45: 711-1004 (page 841, Combination in C. (Crematogaster))

References based on Global Ant Biodiversity Informatics

• Borowiec L. 2014. Catalogue of ants of Europe, the Mediterranean Basin and adjacent regions (Hymenoptera: Formicidae). Genus (Wroclaw) 25(1-2): 1-340.
• Collingwood C. A. 1985. Hymenoptera: Fam. Formicidae of Saudi Arabia. Fauna of Saudi Arabia 7: 230-302.
• Collingwood, C. A. and D. Agosti. 1996. Formicidae (Insects: Hymenoptera) of Saudi Arabia (Part 2) Fauna of Saudi Arabia 15: 300-385.
• Collingwood, C. A., and Donat Agosti. "Formicidae (Insecta: Hymenoptera) of Saudi Arabia (Part 2)." Fauna of Saudi Arabia 15 (1996): 300-385.
• Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)—Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
• Menozzi C. 1930. Formiche della Somalia italiana meridionale. Memorie della Società Entomologica Italiana. 9: 76-130.
• Menozzi C. 1939. Hymenoptera Formicidae. Missione Biologica nel Paese dei Borana. 3: 97-110.
• Sharaf M. R., B. L. Fisher, H. M. Al Dhafer, A. Polaszek, and A. S. Aldawood. 2018. Additions to the ant fauna (Hymenoptera: Formicidae) of Oman: an updated list, new records and a description of two new species. Asian Myrmecology 10: e010004
• Sharaf M. R., S. A. Aldawood, and F. Hita Garcia. 2019. Review of the Arabian Crematogaster Lund (Hymenoptera, Formicidae), synoptic list, distribution, and description of two new species from Oman and Saudi Arabia. ZooKeys 898: 27-81
• Soulié J., and L. D. Dicko. 1965. La répartition des genres de fourmis de la tribu des "Cremastogastrini" dans la faune éthiopienne et malgache. Hymenoptera - Formicoidea - Myrmicidae. Ann. Univ. Abidjan Sér. Sci. 1: 85-106.
• Stanton, M.L., T.M. Palmer and T.P. Young. 2002. Competition-Colonization Trade-Offs in a Guild of African Acacia-Ants. Ecological Monographs 72(3):347-363
• Stanton, M.L., T.M. Palmer and T.P. Young. 2005. Ecological barriers to early colony establishment in three coexisting acacia-ant species in Kenya. Insectes Sociaux 52:393-401
• Weber N. A. 1943. The ants of the Imatong Mountains, Anglo-Egyptian Sudan. Bulletin of the Museum of Comparative Zoology 93: 263-389.
• Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004